Sophisticated automatic transmissions for vehicles are typically operated by complex hydraulic systems. Hydraulic systems for vehicular transmissions require a source of hydraulic fluid, a pump to pressurize that fluid and some means, such as a pressure regulator, to control the "line pressure" output to the transmission. One of the primary functions of the pressurized hydraulic fluid is to operate numerous torque transfer devices--i.e., clutch and brake assemblies--which determine the drive gear ratios by which the torque generated by the vehicle engine is transmitted to the wheels or the like. Some of the pressurized fluid may also be employed to lubricate the transmission and the associated mechanism.
Even the most routine movement of the transmission selector lever by the vehicle operator actuates a "manual valve" which directs the pressurized hydraulic fluid to at least one or more specific torque transfer devices which exhaust the pressurized fluid from one or more of the other torque transfer devices. The state of the several torque transfer devices utilized by the transmission--i.e., whether they are pressurized or depressurized--determines the gear ratio provided by the transmission.
Assuming that the operator has positioned the selector lever, such that the manual valve effects a transmission output which moves the vehicle forwardly, as the vehicle accelerates, a succession of shifts will automatically be effected to shift the transmission through a succession of drive ratios. The signal which evidences the vehicle speed is often supplied by a governor assembly that generally includes a regulating valve to supply a governor output signal pressure, the magnitude of which is reflected by the speed at which the transmission output shaft is rotating. The output signal pressure from the governor may, in turn, be directed to another valve which controls the shift by directing pressurized hydraulic fluid to or from those torque transfer devices which effect the shift to the next successive gear ratio. Each gear ratio requires actuation of its own combination of torque transfer devices, and some provision is generally required to deactivate certain other torque transfer devices in order to accomplish the desired shift.
Sophisticated transmission controls also include a provision to alter the vehicular speed at which any given shift is effected. The transmission controls which incorporate speed response as one of the contributing factors in determining when a shift is to be accomplished generally employ a modulator valve. The modulator valve provides a signal pressure to the required shift valves in response to engine vacuum. The modulator valve is generally operated by engine vacuum or throttle position.
The foregoing brief resume is presented to emphasize the complexity of hydraulic systems employed to control vehicular transmissions. The more subtle the reaction required by the transmission in response to operation of the vehicle, the more complex the hydraulic control system becomes. Even so, the complex valving, together with the required maze of passages, are generally contained within a single valve assembly that is secured, for example, to a supporting surface provided on the transmission case.
One face of a typical prior art oil pump and transmission control valve body 10 is depicted in FIG. 1. Both faces of the valve body 10 are generally of comparable complexity, and the depicted face 11 is, therefore, representative of that complexity. Specifically, face 11 is provided with a maze of surface passages, generally referred to as wormtracks 12 which provide the required communication along the opposite faces of the valve body in order to achieve communication with the components contained within the valve body 10. A supporting surface (not shown in FIG. 1) to which the valve body 10 may be secured is generally provided on the transmission case. The supporting surface, as well as the cover plate (also not shown), which matingly engage the opposite faces of the valve body 10, are similarly provided with wormtracks that cooperatively interact with the wormtracks recessed into the faces of the valve body 10. Passageways may penetrate the valve body 10, as required, to effect communication between appropriate wormtracks recessed within the opposite faces of the valve body 10.
Various chambers and bores are disposed between and generally in parallel relation with the opposite faces of the valve body 10 to house the several valve members and the associated components that are received within the transmission control valve body 10. FIG. 1 depicts, in exploded plan, a representative sampling of the components that are operatively received within the various chambers and bores that extend within the valve body 10. Starting at the one o'clock position on FIG. 1, one can observe the throttle valve member 13, the throttle valve spring 14, the throttle valve plunger 15 and the throttle valve plunger bushing 16 which are received within a laterally extending bore (not shown) that penetrates the right side 18 of the valve body 10. A retainer pin 19 secures those components within that bore. Continuing clockwise on FIG. 1, the next bore (also not shown) that penetrates the right side 18 of the valve body 10 receives a pressure regulator valve 20, a pressure regulator valve spring 21, a pressure regulator isolator spring 22, a reverse boost valve 23, a pressure regulator and reverse boost valve bushing 24, a boost valve 25, an isolator valve bore plug 26 and a valve retainer ring 28, all of which are secured by the retainer pin 29.
The 3-2 shift control valve 30, its biasing spring 31 and a spring retainer sleeve 32 are received within an independent bore (not shown) that penetrates the lower portion on the right side 18 of the valve body 10. The Lo blow-off ball 33, its biasing spring 34 and a retainer plug 35 are received in another bore (not shown) which penetrates the lower side 36 of the valve body 10, also as viewed in FIG. 1.
A bore also penetrates the lower portion on the left side 38 of the valve body 10, to receive a 1-2 shift valve 40, a 1-2 throttle valve 41, a 1-2 throttle valve spring 42 and a 1-2 throttle valve bushing 43, all of which are maintained within that bore by a retainer pin 44. Another bore (not shown) also penetrates the lower portion on the left side 38 of the valve body 10 to receive a 2-3 shift valve 45, a 2-3 throttle valve 46, a 2-3 throttle valve spring 48 and a 2-3 throttle valve bushing 49, all of which are secured within that bore by a retainer pin 50.
A first bore (also not shown) penetrates the middle portion on the left side 36 of the valve body 10 to receive a 1-2 accumulator valve 51, a 1-2 accumulator bushing 52, a 1-2 accumulator spring 53, a valve bore plug 54 and a retainer pin 55. A second bore penetrates the middle portion on the left side 38 of the valve body 10 to receive a pressure relief ball 56, a pressure relief biasing spring 58 and a spring retainer sleeve 59. In addition, a third bore penetrates the middle portion on the left side 38 of the valve body 10 to receive a T.V. shift valve 60, a T.V. shift spring 61, a valve bore plug 62 and a retainer pin 63.
A pressure regulator bore plug 64 and an associated retainer 65 close the bore that extends through the upper portion on the left side 38 of the valve body 10. Finally, a line boost valve 66, a line boost valve plug 68 and a retainer pin 69 are received within a bore that penetrates the top surface 70 of the valve body 10.
Most important to the present invention is the fact that the prior art transmission valve bodies, as well as the cover plates employed therewith, must accommodate a considerable number of bolts, such as the seventeen bolts 75A through 75Q depicted, required effectively to secure the valve body 10 and its cover plate to the supporting structure on which they are mounted. It should be appreciated that each mounting bolt 75 must penetrate the valve body 10 with sufficient clearance from adjacent valve chambers and bores (not shown), as well as the wormtracks 12, to permit the bolts 75 to secure the valve body 10 to its supporting surface without distorting or damaging the valve body 10 itself as well as to assure that the wormtracks 12 will be effectively sealed from adjacent wormtracks as well as from the environment in which the transmission is operated.
As previewed above, and in the detailed description which follows, a particular structural member, component or arrangement may be employed at more than one location. When referring generally to that type of structural member, component or arrangement, a common numerical designation shall be employed. However, when one of the structural members, components or arrangements so identified is to be individually identified, it shall be referenced by virtue of a letter suffix employed in combination with the numerical designation employed for general identification of that structural member, component or arrangement. Thus, there are a plurality of bolts which are generally identified by the numeral 75, but the specific individual bolts are, therefore, identified as 75A, 75B, 75C, etc., in the specification and on the drawings. This same suffix convention shall be employed throughout the specification.